Filter capable of trapping carcinogens and toxic chemicals and manufacturing method thereof

ABSTRACT

A filter has a urethane-based main chain having a repeat unit of the formula,  R′—NH—COO—R—O—NH   n , wherein the R group and the R′ group are an aliphatic chain and an aromatic group respectively. The R group, R′ group, and —NH— moiety in the repeat unit serve as reactive radicals for trapping cyanides, phenols, or polynuclear aromatic compounds, wherein the reactive radicals are revealed through an extraction process to remove a plurality of contaminants from the urethane-based main chain.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. application Ser. No.10/250,058, filed Jun. 2, 2003.

The present application claims priority under 35 U.S.C. § 120 to U.S.patent application Ser. No. 09/252,334, filed Feb. 18, 1999 and nowissued as U.S. Pat. No. 6,273,095, which in turns claims priority under35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 60/093,330,entitled SAFE CIGARETTE FILTER, filed Jul. 20, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing a filtercapable of removing cyanides and polynuclear aromatic compounds fromcigarette smoke, and more specifically, to a method for manufacturing afilter capable of removing cyanides, phenols, and polynuclear aromaticcompounds from air.

2. Description of the Prior Art

People begin smoking cigarettes for a variety of reasons. Smoking hasbeen portrayed as being heroic, cool and as enhancing sexual appeal. Forsome people, smoking also serves to soothe tension, anxiety, orloneliness. However, as is commonly known, cigarette smoke contains theaddictive compound nicotine. Addiction to nicotine makes it verydifficult for smokers to stop smoking cigarettes, even though manyrealize that smoking will adversely affect their health.

The serious negative health effects of smoking are generally caused bychemicals in tobacco smoke other than nicotine. Among these arepolynuclear aromatic compounds, which are carcinogens suspected to causeor contribute to a variety of cancers. The formation of polynucleararomatic compounds in cigarette smoke is the result of incompletecombustion of the cigarette due to short burning resident time.Furthermore, polynuclear aromatic compounds harm not only smokers, butalso the surrounding environment and people who inhale them assecond-hand smoke. Furthermore, tobacco smoke also contains cyanides, ahighly toxic compound which causes adverse health effects in smokers andthose inhaling second-hand smoke.

The tobacco industry has attempted to alleviate the problems caused bypolynuclear aromatics and cyanides by incorporating filters intocigarettes to remove these compounds when a smoker inhales. Thesefilters are typically made of cellulose-based materials. The filters areeffective in removing some of the toxic chemicals from tobacco smoke,but a substantial amount still passes through the filter. Consequently,there exists a need for improving filters for cigarettes and othertobacco products, which are more efficacious in removing toxic andcarcinogenic chemicals from tobacco smoke. Moreover, to encourage use ofsuch a filter, the filter should not interfere with those aspects ofsmoking which smokers desire, including the taste and nicotine contentof the smoke.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to provide amethod for manufacturing a filter capable of removing cyanides, phenols,and polynuclear aromatic compounds from air.

It is another objective of the present invention to provide a method formanufacturing a filter capable of selectively removes polynucleararomatic compounds and low molecular weight compound includingmono-aromatic compounds and cyanides from tobacco smoke, whilepermitting most of the nicotine and flavor-enhancing molecules in thesmoke to pass through. Because of this, people smoking tobacco productswho use the filter of the present invention may enjoy the smokingexperience, but with less exposure to the dangerous components oftobacco smoke.

According to the claimed invention, the filter comprises aurethane-based main chain having a repeat unit of the formula,

R′—NH—COO—R—O—NH

_(n), wherein the R group and the R′ group are an aliphatic chain and anaromatic group respectively. The R group, R′ group, and —NH— moiety inthe repeat unit are reactive radicals for trapping cyanides, phenols, orpolynuclear aromatic compounds, wherein the reactive radicals is formedthrough an extraction process to remove a plurality of contaminants fromthe urethane-based main chain.

According to the present invention, the method for manufacturing afilter capable of removing cyanides, phenols, or polynuclear aromaticcompounds from air is provided. Firstly, a polyurethane materialincluding a urethane-based main chain having a repeat unit of theformula,

R′—NH—COO—R—O—NH

_(n), with a plurality of contaminants absorbed around theurethane-based main chain is provided. Then, an extraction is performedto remove the contaminants from the urethane-based main chain so as toform a plurality of reactive radicals for trapping cyanides, phenols, orpolynuclear aromatic compounds.

In one aspect of the present invention, the polyurethane filtercomprises a tubular body with a proximal and a distal end. The tubularbody is formed out of middle-density cellular polyurethane foam. Thefoam is pre-treated to increase the number of available reactiveradicals for absorbing polynuclear aromatic compounds, perniciousmono-aromatic compounds, and cyanides. When used with a cigarette havinga conventional filter, the polyurethane foam filter having anuncompressed volume of about 2 cubic centimeters absorbs about 60% ofthe polynuclear aromatic compounds and cyanide contained in cigarettesmoke which contact the filter, but permits about 75% of the contactingnicotine in the smoke to pass through.

In another embodiment, a polyurethane foam filter of the presentinvention is substantially substituted for a conventional cigarettefilter and is incorporated into the body of the cigarette as part of themanufacturing process. In this embodiment, a polyurethane foam filter,which prior to incorporation into the cigarette has an uncompressedvolume of about 2-cubic centimeters, absorbs at least 74% of thepolynuclear aromatic hydrocarbons contacting the filter in thecigarette, but permits about 75% of the nicotine contacting the filterto pass through. In another embodiment, a similarly sized polyurethanefoam filter of the present invention is completely substituted for aconventional cigarette filter and absorbs at least 90% of thepolynuclear aromatic hydrocarbons which pass through the filter.

In another aspect of the present invention, there is provided animproved filter for removing carcinogenic and toxic compounds fromtobacco smoke. The invention comprises a pre-treated polyurethane foambody which absorbs 30-45% of contacting total polynuclear aromaticcompounds per cubic centimeter of uncompressed polyurethane foammaterial forming the filter, but which permits more than 88% of thecontacting nicotine to pass through unabsorbed per cubic centimeter ofpolyurethane foam material. The improved filter having these propertiesmay be incorporated into a cigarette body, a cigar or a pipe body.

In another aspect of the present invention, there is provided apre-treated polyurethane foam filter which absorbs in aggregate 60%-90%of 2-methylnaphthalene, acenaphthylene, acenaphthene, dibenzofuran,fluorene, phenantherne, anthracene, carbazole, fluoranthene, pyrene,benzo(a)anthracene and chrysene in tobacco smoke passing through thefilter per 2 cubic centimeters of uncompressed foam used to make thefilter.

In another aspect of the present invention, there is provided a methodof making a safer cigarette. The method comprises providing amiddle-density cellular polyurethane foam (PUF), which may then beformed into a cylindrical body to form a filter. The PUF filter is thenpre-treated by cleaning to increase reactive radicals for adsorbing thepolynuclear aromatic compound and cyanide. Alternately, the pre-treatingstep may occur before PUF filter is shaped into the cylindrical body.The cylindrical body is incorporated into a cigarette as a filter suchthat when the cigarette is lit, smoke will pass through the PUF filterprior to being inhaled by a smoker.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a cigarette incorporating the filterof the present invention into the body of the cigarette.

FIG. 2 illustrates extracted polyurethane foam having reactive radicalsfor trapping cyanides and phenols via hydrogen bonds.

FIG. 3 is a cross-sectional view of a filter of the present inventionincorporated into a cigarette holder that may be attached and detachedfrom cigarettes.

FIG. 4 illustrates the comparison of polynuclear aromatic emissions (inng) of cigarette smoke from a filterless cigarette, a conventionalcigarette with a filter, and a cigarette with a PUF filter.

FIG. 5 is analytical results of experiment 1.

FIG. 6 is analytical results of experiment 2.

FIG. 7 is analytical results of experiment 4.

FIG. 8 is a summary of percentage of total polynuclear aromaticsabsorbed by a PUF filter.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a cigarette 10 incorporating apolyurethane foam (PUF) filter 35 of the present invention. Althoughillustrated and described in the context of a tobacco cigarette, itshould be understood by those of skill in the art that the filter of thepresent invention might be readily incorporated in a mask or otherfiltering device that is applied to filter out pollutants or poisonousgas from air. Moreover, although the filter of the present invention isdescribed as having a tubular or cylindrical shape, it should beappreciated by those of skill in the art that the filters of the presentinvention may take other shapes, including square, rectangular,spherical, and the like.

As shown in FIG. 1, the cigarette 10 comprises a cylindrical body 12formed from a paper product, which is wrapped around tobacco 20. Thecigarette 10 has a distal end 14 and a proximal end 16. In this respect,the cigarette 10 may be any conventional cigarette known to those ofskill in the art, such as those made and sold today by the tobaccoindustry. The cigarette 10 may also incorporate a conventional filter 25near the proximal end 16 thereof. The conventional filter 25 is used incigarettes sold today, such as cellulose-based filters, but may bereduced in size when used in conjunction with the PUF filter 35 of thepresent invention, as described below.

Polyurethane foam (PUF) has been used by United States EnvironmentalProtection Agency to trap polynuclear aromatic compounds,polychlorinated biphenyls, dioxins/furans, and the like, from air withreasonably high efficiency. These compounds have an affinity forpolyurethane, and tend to be absorbed onto the surface of polyurethane.However, the polyurethane foam cannot efficiently absorb low molecularweight compounds, including cyanides, phenols, and aromatic compoundswith a single aromatic ring. Accordingly, the present invention makesthe polyurethane foam be pre-treated to form the PUF filter 35 capableof effectively removing not only the polynuclear aromatic compounds butalso the low molecular weight compounds from cigarette smoke or air.

As shown in FIG. 1, the PUF filter 35 is incorporated at a proximal end16 by being wrapped with a paper product. Preferably, the cigarette 10also incorporates a portion of the conventional filter 25, and the PUFfilter 35 is positioned proximal to the conventional filter 25 at theproximal end 16. When this two-filter combination is used, theconventional filter 25 will function to protect the PUF filter 35 fromburning when the tobacco is completely combusted. In this respect, it ispreferred that the conventional filter 25 have a diameter approximatelythat of the cigarette body 12, and a length of from about 1 mm to about4 mm, and more preferably from about 2 mm to about 3 mm. As statedabove, the conventional filter 25 may be made of cellulose-basedmaterials. However, other types of materials known to those of skill inthe art may be used in place of the conventional filter 25 to protectthe PUF filter 35, provided that the materials are compatible withpolyurethane foams. Moreover, in some embodiments, it may be desirableto eliminate the conventional filter 25, and use only the PUF filter 35at the proximal end 16 of the cigarette 10.

As described above, the PUF filter 35 is formed from the polyurethanefoam, which has extensive cellular structure and is preferably selectedfrom middle-density polyurethane foam having a density of from about0.01 to about 0.05 grams per milliliter. More preferably, thepolyurethane foam used will have a density of from about 0.02 to about0.04 grams per milliliter. However, it should be understood by those ofskill in the art that any polyurethane foam with a cellular structureand appropriate density that permits cigarette smoke to pass through maybe used with the present invention, provided that it conforms to theteachings herein. One kind of polyurethane foam found suitable for usein the present invention may be purchased from San Antonio FoamFabricator, Product No. NA-85. This foam has a cellular structure and adensity of 0.0302 grams per milliliter. Additionally, the PUF filter 35could also be formed from polyurethane fibers, which could achieve thegoal of filtering out low molecular weight compounds, as well aspolyurethane foams.

The PUF filter 35 may vary in size and dimension as desired by thecigarette manufacturer. Preferably, the PUF filter 35 has approximatelythe same diameter as the cigarette in which it is incorporated and alength similar to conventional filters used today for cigarettes. Thislength may average from about 1 to 2.5 centimeters. Furthermore, becausethe beneficial effects of the present invention result from thepolyurethane foam absorbing the harmful compounds, providing a largerpolyurethane foam filter will tend to increase the total percentage ofthese compounds absorbed. As described in more detail below, thepolyurethane foam formed into the filter having a volume of two cubiccentimeters has been shown to successfully absorb about 75% of thepolynuclear aromatic compounds passing through it.

As mentioned above, the present invention makes the polyurethane foam bepre-treated to form the PUF filter 35 capable of effectively trappingnot only the polynuclear aromatic compounds but also the low molecularweight compounds, including cyanides, phenols, and aromatic compoundswith a single aromatic ring. One method that has been shown useful toachieve this is Soxhlet extraction, which cleans the polyurethane foamand therefore increases the number of reactive radicals for trappingcyanides, phenols, and polynuclear aromatic compounds. In the Soxhletextraction, a solvent containing 6% ether in hexane is evaporated from asolvent reservoir. The solvent vapor is then condensed into a chambercontaining the polyurethane foam to be treated. The polyurethane foam inthe chamber is gradually immersed in the condensed solvent until it istotally immersed. Most of the contaminants on or in the polyurethanefoam will be extracted into the solvent. The solvent in the chamber isthen siphoned through a tube down to the solvent reservoir at thebottom. The solvent evaporated out of the solvent reservoir is alwayspure and free from contaminants from the polyurethane foam. Therefore,only contaminant-free solvent is condensed into the chamber and allcontaminants from the polyurethane foam accumulate in the reservoir. Thesolvent in the chamber is siphoned approximately once every hour for 16hours. After the Soxhlet extraction, excess solvent is removed from thepolyurethane foam by blowing it to dryness in nitrogen.

Before the polyurethane foam is pre-treated, the polyurethane foamoriginally comprises a urethane-based main chain and a plurality ofcontaminants absorbed by the urethane-based main chain. Usually, theurethane-based main chain has a repeat unit of the formula:

R′—NH—COO—R—O—NH

_(n), wherein the R group is an aliphatic chain, such as n-octyl, andthe R′ group is an aromatic group, such as tolyl. In addition, thecontaminants absorbed by the urethane-based main chain include phenols,such as 6-tert-butyl-2,4-dimethylphenol and butylated methyl phenol,tinuvin, monomers, dimers, oligomers,4,4,5,6-tetramethyltetrahydro-1,3-oxazin-2-thione, and so on.Furthermore, it is observed that the NH moieties of the urethane-basedmain chain are originally occupied by 6-tert-butyl-2,4-dimethylphenol,butylated methyl phenol and another unknown phenol, while the R groupand the R′ group are originally absorbed by tinuvin, monomers, dimers,oligomers, and 4,4,5,6-tetramethyltetrahydro-1,3-oxazin-2-thione.

It should be noticed that after the polyurethane foam is extracted byuse of the Soxhlet extraction, those unwanted contaminants are removedfrom the polyurethane foam, thus forming the urethane-based main chainhaving a plurality of reactive radicals, wherein each radical has atleast one unpaired electron and is highly reactive. Referring to FIG. 2,FIG. 2 illustrates extracted polyurethane form having reactive radicalsfor trapping cyanides and phenols via hydrogen bonds. As shown in FIG.2, the urethane-based main chain of the polyurethane foam is formedafter the polyurethane foam is pre-treated by the Soxhlet extraction.Additionally, as shown in FIG. 2, the nitrogen atom of the NH moiety hasa lone pair electron that can absorb a hydrogen atom of cyanides orphenols due to hydrogen bonds, so that the NH moieties are reactiveradicals for trapping cyanides and phenols. Furthermore, after theremoval of the contaminants, the R group and the R′ group are availablefor absorbing polynuclear aromatic compounds via van der Waalsattraction that is molecular attracting force between neutral andnon-polar organic portions. Therefore, the R group and the R′ group arealso reactive radicals for absorbing polynuclear aromatic compounds. Asa result, the polyurethane foam that is pre-treated by the Soxhletextraction can trap not only polynuclear aromatic compounds but also thelow molecular weight compounds, including cyanides, phenols, andaromatic compounds with a single aromatic ring. However, most of thenicotine, which is a substituted pyridine, and some small volatilemolecules contributing to the smoke's flavor in the smoke still can passthe pre-treated polyurethane foam, so that a pleasant sensation of asmoker may not be decreased.

Other methods suitable to pre-treat the polyurethane foam and thereforeincrease its reactive radicals for trapping polynuclear aromaticcompound and toxic compound may include extraction using solvents otherthan 6% ether in hexane, such as methylene chloride, hexane, lighthydrocarbon based solvents, and mixtures of the foregoing. Furthermore,supercritical fluid extraction, steam distillation, hot solventextraction and any other suitable organic extraction technique may alsobe used.

Referring to FIG. 3, there is shown as an alternative embodiment of thePUF filter of the present invention, where the PUF filter isincorporated into a cigarette holder 50 which can be removably attachedto a conventional cigarette 100. As shown in FIG. 3, the cigarette 100comprises a tubular body composed of a paper product wrapped aroundtobacco 120. A conventional filter 125 may be incorporated into thetubular body at a proximal end 116, but this is not required. Thecigarette holder 50 has a generally tubular body 55, which extends froma distal end 54 to a proximal end 56, and as shown in FIG. 3, tapers toa smaller diameter beginning at a point 58 to form a smaller diametermouthpiece opening 65 at the proximal end 56. The cigarette holder 50may take a variety of other forms, as may be aesthetically pleasing orto provide ergonomic benefits. Furthermore, the holder 50 may be formedfrom any of the variety of materials known to those of skill in the artto be useful for manufacture of cigarette holders, such as metals andplastics. The holder 50 may also vary in length, diameter andappearance, as desired by its manufacturer to provide for desiredaesthetic and ergonomic properties.

For purposes of the present invention, the holder 50 merely providesstructure to encompass a polyurethane foam filter and provide an airwaychannel so that cigarette smoke inhaled by a smoker must pass throughthe polyurethane foam filter. For the holder 50, such an airway channelis defined by a lumen 60, which extends from the proximal end 56 to thedistal end 54.

The lumen 60 has a larger inner diameter at the distal end 54, and isproportioned to receive the proximal end of a conventional cigarette.Preferably, the lumen 60 is dimensioned to snugly fit over aconventional cigarette, such that a cigarette inserted into the lumen 60will be held firmly in place, but may be removed with minimal effort bya person. Incorporated into the lumen 60 is a polyurethane foam (PUF)filter 35 of the present invention. Preferably, the PUF filter 35 hasbeen pre-treated to increase the number of reactive radicals forabsorbing polynuclear aromatic compounds and cyanides, as describedabove. The PUF filter 35 should have a diameter to fill the entirely ofthe lumen 60, such that any cigarette smoke which passes through thelumen 60 to the mouthpiece opening 65 must pass through the PUF filter35. This may be accomplished by forming the PUF filter 35 to have anuncompressed diameter slightly greater than that of the lumen 60, andthen slightly compressing the PUF filter 35 so that it fits snugly inthe lumen 60.

In this manner, polynuclear aromatic compounds, cyanides, andmono-aromatic compounds which contact and bond to the reactive radicalsin PUF filter 35 will be removed from cigarette smoke as they passthrough the PUF filter 35. Because these compounds are removed from thesmoke prior to being inhaled by a smoker, they should not adverselyaffect the smoker's health, and should not adversely affect bystander'shealth through second-hand smoke. However, as described previously, mostof the nicotine and flavor-enhancing molecules present in the smoke willpass through the PUF filter 35 to mouthpiece opening 65. Thus a pleasantsensation of a smoker may not be decreased.

The selective absorption properties of the polyurethane foam of thepresent invention are demonstrated in the following experimentalexamples.

EXPERIMENTAL EXAMPLES

A set of cylindrical PUF filters was cut from a sheet of NA-85polyurethane foam. Each cylindrical PUF filter had an outside diameter(O.D.) of about 1 cm and a height of 1 inch (2.54 cm), and therefore inan uncompressed state had a volume of about 2 cubic centimeters. The PUFfilters were then pre-treated to increase reactive radicals forabsorbing polynuclear aromatic and cyanide by Soxhlet extraction asdescribed above with 6% ether in hexane for 16 hours. The PUF filterswere then blown to dryness using nitrogen until all of the solvent wasremoved.

One of the PUF filters was slightly compressed and then inserted intoclean 6.7 inch long and 0.8 cm inside diameter(I.D.)glass tubing with1.8 cm tapered end. The filter end of a Dorall Full Flavor Premium™cigarette was inserted into the other end of the glass tubing. Becausethe O.D. of PUF filter was slightly larger than the I.D. of the glasstubing, the PUF filter fit snugly in the tubing and all tobacco smokepassing through the glass tubing passed through the PUF filter. Teflontape was wrapped around the filter end of the cigarette and glass tubingto seal them together. All of the Dorall cigarettes used in the studywere from the same package.

The glass tubing was then connected horizontally to an inlet of a 100 mLimpinger manufactured by Ace Glassware. The impinger used in this studywas designed to trap polynuclear aromatics, cyanide and tar passingthrough the PUF filter.

All the trapped polynuclear aromatics, cyanide and tar in the impingerwould have been inhaled by a smoker if the cigarette had been smoked.The outlet of the impinger was connected to a hand-pump (Mityvac #OB61,Neward Enterprises, Cucamonga, Calif.). Each press of the hand-pumppumped approximately 30-40 mL of air through the cigarette to simulatean inhalation by an average smoker. The impinger was then immersed inliquid argon and the cigarette was lit. Continuous pumping was thenapplied to the hand pump to suck the air through the cigarette.Cigarette smoke went through the PUF filter, impinger, and hand-pumpbefore venting into a fume hood. The hand-pump was continuously pumpedby hand until the cigarette had 4 mm of length left. The approximatesampling time was one minute.

After sampling, the impinger was filled with 70 mL of methylene chlorideto dissolve the tar collected and left overnight. Afterwards, themethylene chloride was poured into a vial. The impinger was then rinsedwith methylene chloride to capture any tar remaining in the impinger,and the rinse was poured into the same vial. The methylene chloridesolution was concentracted down to 20 mL prior to gas chromatography andmass spectroscopy (GC/MS) analysis. A 4 mL sample of the methylenechloride solution was blown down with nitrogen to remove all methylenechloride and the residue or tar was weighed to five decimal places. Thetar was weighed twice: one at five minutes after the first weighing andthe second in the next day. The average of the tar weights is reportedin FIG. 5.

The PUF filter used in the experiment was removed from the glass tubing.The PUF filter was then Soxhlet extracted using methylene chloride andthe extract was concentrated to 5 mL before GC/MS analysis. Onemilliliter of the extract was used to measure the weight of tar by themethod mentioned above.

This experiment was repeated as described above, except that in thesecond experiment the cigarette was completely burned. The conventionalcigarette filter burned slightly before end of the sampling.

The same procedure as the first experiment was performed four more timeswith the following changes to the protocol:

Experiment 3 was with a conventional filtered cigarette and without aPUF filter,

Experiment 4 was with a partially filtered cigarette and a PUF filter,

Experiment 5 was with an unfiltered cigarette and without a PUF filter,

Experiment 6 was with a PUF filter, but without a cigarette (laboratoryblank).

In Experiment 4, 75% of the regular cigarette filter was removed andreplaced with a PUF filter without tearing the paper holding thecigarette filter. The remaining 25% of the regular cigarette filtersegregated the cigarette from PUF filter to prevent burning of the PUFfilter during this experiment.

RESULTS

No compounds were detected in the laboratory blank in either theimpinger and PUF filter (Experiment 6).

FIG. 4 shows a table comparing the polynuclear aromatics and tar trappedin the impinger while (1) using the cigarette with only a conventionalcigarette filter; (2) using a partially filtered cigarette with only aPUF filter; and (3) using the cigarette without any filter. As shown inFIG. 4, the PUF filter of the present invention is significantly betterthan regular cigarette filters in removing toxic polynuclear aromaticssuch as 2-methylnaphthalene, acenaphthylene, acenaphthene, dibenzofuran,fluorene, phenanthrene, anthracene, carbazole, fluoranthene, pyrene,benzo(a)anthracene and chrysene. This is demonstrated from comparing theweight of polynuclear aromatic compounds found in the impinger when aconventional filter was used to those found when the PUF filter wasused. However, the nicotine and cotinine (oxidation product of nicotine)emissions from the cigarette with PUF filter are roughly the same as acigarette with the regular cigarette filter.

The percentage of polynuclear aromatics and tar removed in the otherexperiments using the PUF filter are listed in FIG. 5 to FIG. 7 andsummarized in FIG. 8. In those experiments where a 2 cubic centimeterPUF filter is used in conjunction with a regular cigarette filter, thePUF filter of the present invention removed about 60% of polynucleararomatic compounds in cigarette smoke which contacted it, or 30% percubic centimeter of uncompressed foam material. Furthermore, the PUFfilter permitted about 75% of the nicotine in cigarette smoke whichcontacted the PUF filter to pass through. In those embodiments in whichabout 75% of the regular filter of a cigarette was replaced with the PUFfilter, the PUF filter removed about 74% of polynuclear aromaticcompounds contacting it, or about 37% per cubic centimeter ofuncompressed foam material, but still permitted about 75% of thenicotine in cigarette smoke to pass through.

As noted above, a PUF cylindrical body having a volume of 2 cubiccentimeters in its uncompressed state was slightly compressed andinserted into the experimental apparatus to function as a filter. InExperiment 4, this PUF filter removed 74% of the polynuclear aromaticcompounds when used without a complete regular filter (75% of theregular filter removed), compared to only 60% when a complete regularfilter was used as in Experiment 1. This may be due to the fact thatthere are significant amounts of glycerol triacetate embedded in mostregular cigarette filters. It was observed that the amount of glyceroltriacetate found in each experiment was approximately the same as thatof nicotine. The glycerol triacetate emitted during these experimentsmay be trapped by the PUF filters. The trapped glycerol triacetate wouldoccupy many of the reactive radicals on the PUF filter, which would beotherwise available for polynuclear aromatics. Therefore, with acomplete regular cigarette filter, the efficacy of the PUF filtertrapping polynuclear aromatics was reduced, compared to when used withonly a partial (25%) regular cigarette filter. In view of these results,it is expected that the percentage of polynuclear aromatic compoundsabsorbed by the PUF filter would increase from 74% to about 80-90% per 2cubic centimeters of uncompressed PUF starting material, if the PUFfilter is used without any conventional cigarette filter, or if theamount of glycerol triacetate in regular cigarette filter is reduced.

Three more experiments were performed to determine the efficiency of PUFfilters in removing cyanide from cigarette smoke. These experiments wereperformed in the same manner as the first experiment. However, insteadof 70 mL of methylene chloride to dissolve tar trapped in the impingerby liquid argon, 37 mL of 0.25 N sodium hydroxide was added to impingerto rinse and convert trapped inorganic cyanide compounds to cyanideanion, which was then analyzed by ion chromatography. For a cigarettewith conventional filter but without PUF filter, 660 micrograms of totalcyanide were found in the 37 mL impinger rinsing solution. This was fromthe smoke that would have been inhaled by the smoker if the cigarettehad been smoked. However, for a cigarette with both regular filter andPUF filter, 250 micrograms of total cyanide were found in the 37 mLimpinger rinsing solution. For a blank, an unlit cigarette with regularfilter but without PUF filter was used. For the blank, cyanide was notfound at the detection limit of 3.7 micrograms in the 37 mL impingerrinsing solution. These experiments indicate that approximate 62% oftotalcyanide in cigarette smoke passing through the PUF filter wasremoved by a PUF filter of the present invention.

Because the PUF filter used in this study are made from medium densitypolyurethane foam, the pressure drop across the PUF filter is much lowerthan regular cigarette filter. Most smokers familiar with a conventionalcigarette filter may not be familiar with a filter which has a lowpressure drop. Consequently, they may inhale larger quantities of smokeat the beginning. Therefore, smokers may either be informed of the lowerpressure drop, or use a PUF filter as an additional filter after theregular cigarette filter. In the latter way, the PUF filter may beinserted in a cigarette holder and then a cigarette with regular filteris inserted into the cigarette holder before smoking.

Although this invention has been described in terms of certain preferredembodiments, other embodiments will be apparent to those of ordinaryskill in the art in view of the disclosure herein are also within thescope of this invention. Accordingly, the scope of the invention isintended to be defined only by reference to the appended claims.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A filter comprising a urethane-based main chain having a repeat unitof the formula,

R′—NH—COO—R—O—NH

_(n), the R group and the R′ group being an aliphatic chain and anaromatic group respectively, wherein the R group, R′ group, and —NH—moiety in the repeat unit of the urethane-based main chain are reactiveradicals for trapping cyanides, phenols, or polynuclear aromaticcompounds.
 2. The filter of claim 1, wherein the nitrogen atom of thereactive radical —NH— moiety in the repeat unit,

R′—NH—COO—R—O—NH

_(n), has a lone pair electron for binding the phenols and the cyanidesvia hydrogen bonds.
 3. The filter of claim 1, wherein the reactiveradicals R group and R′ group absorb the polynuclear aromatic compoundsvia van der Waals attraction.
 4. The filter of claim 1, wherein thereactive radical R group comprises n-octyl.
 5. The filter of claim 1,wherein the reactive radical R′ group comprises tolyl.
 6. The filter ofclaim 1, wherein the reactive radicals are formed through an extractionprocess to remove a plurality of contaminants originally bonded with thereactive radicals in the repeat unit of the urethane-based main chain.7. The filter of claim 6, wherein the urethane-based main chain havingthe contaminants bonded with the reactive radicals in the repeat unitbefore the extraction process is a polyurethane foam or a polyurethanefiber.
 8. The filter of claim 7, wherein the polyurethane foam orpolyurethane fiber has a density of between about 0.01 g/ml to about0.05 g/ml.
 9. The filter of claim 6, wherein the reactive radical —NH—moiety is originally occupied by the contaminants comprising phenolsbefore the extraction process.
 10. The filter of claim 9, wherein thephenols comprise 6-tert-butyl-2,4-dimethylphenol and butylated methylphenol.
 11. The filter of claim 6, wherein the reactive radicals R groupand the R′ group are originally occupied by the contaminants comprisingtinuvin, monomers, dimers, oligomers, and4,4,5,6-tetramethyltetrahydro-1,3-oxazin-2-thione before the extractionprocess.
 12. The filter of claim 6, wherein the extraction is a Soxhletextraction.
 13. The filter of claim 12, wherein the Soxhlet extractionuses a solvent containing 6% ether in hexane to extract the contaminantsfrom the polyurethane material for revealing the urethane-based mainchain.
 14. The filter of claim 12, wherein the Soxhlet extraction uses asolvent comprising methylene chloride, hexane, light hydrocarbon basedsolvents, or mixtures of the foregoing to extract the contaminants fromthe polyurethane material for revealing the urethane-based main chain.15. The filter of claim 6, wherein the extraction is a supercriticalfluid extraction, a steam distillation, a hot solvent extraction, or anorganic extraction.
 16. The filter of claim 6, the filter is furtherformed through drying the urethane-based main chain after the extractionprocess.
 17. The filter of claim 1, wherein the polynuclear aromaticcompounds comprise 2-methylnaphthalene, acenaphthylene, acenaphthene,dibenzofuran, fluorene, phenanthrene, anthracene, carbazole,fluoranthene, pyrene, benzo(a)anthracene, and chrysene.